Wireless communications systems are operated worldwide by carriers who charge fees to subscribers for use of wireless services such as interconnect, short message service (SMS), packet data and push-to-talk (PTT). Each wireless communications system services subscribers within a geographic coverage area and operates using one or more wireless technologies such as code division multiple access (CDMA), global system for mobile communication (GSM), time division multiple access (TDMA) or Advanced Mobile Phone Service (AMPS).
PTT services (also known as a walkie-talkie or dispatch services) are currently offered by some wireless carriers, such as Nextel's Direct Connect® service, and new PTT services and technologies have been proposed. Generally, a PTT call provides near-instant, half-duplex communication between a PTT caller and a target group of PTT users. PTT calls are currently limited to calls between wireless users who utilize compatible PTT technologies and are subscribers on the same carrier network. For example, subscribers on a network operated by a first wireless carrier cannot currently engage in PTT calls with PTT subscribers on a network operated by a second wireless carrier.
Solutions have been proposed to connect two or more disparate PTT networks, but such solutions do not efficiently use the resources of each PTT network. For example, iDEN systems use a mobile station identifier for PTT communications known as an Urban Fleet Member Identifier (UFMI). Due to constraints of the iDEN system, there are a limited number of UFMIs available to be assigned, thus imposing scalability limitations when connecting the iDEN network to one or more external networks. Accordingly, a need exists for a PTT inter-working solution that efficiently utilizes iDEN's UFMI address space.